1. Field of the Invention
The present invention relates to a liquid jet recording process where a liquid is ejected to form liquid droplets and projected to a record member, and a liquid jet recording head.
2. Description of the Prior Art
Non-impact recording processes have recently drawn attention since the noise accompanying recording operation is negligibly small.
Among them, ink jet recording process (liquid jet recording processes) which can effect a high speed recording and can record on plain paper without fixation are very powerful processes. Heretofore, a wide variety of the systems and apparatuses therefor have been proposed. Some of them have been practically operated while others are now under development.
Liquid jet recording process disclosed in Japanese Patent Laid Open No. Sho 54-51837, Deutsch Offenlegungsschrift No. 2843064, U.S. Application Ser. No. 948236, filed Oct. 3, 1978, has a feature different from other liquid jet recording methods. The feature is that heat energy is applied to a liquid to produce an actuating force for ejecting the liquid.
The above-mentioned patent applications disclose a recording process in which a liquid causes a change of the state accompanying an abrupt increase in volume by application of heat energy and the actuating force due to the change of the state functions to eject liquid droplets from the orifice at the tip of a recording head and project the droplets to a record receiving member. The recording head comprises a liquid ejecting portion including an orifice for ejecting a liquid droplet. A heat actuating portion communicating with the orifice and having a heating surface adapted to apply heat energy to the liquid, and an electrothermal transducer for generating heat energy which is coupled to the heat actuating portion.
The liquid jet recording process of Deutsch Offenlegungsschrift No. 2843064 is effectively applied to so-called drop-on-demand type recording process and moreover, the recording head can be easily constructed in the form of a high density multiorifice system of a full line type. As the result, images of high resolution and high quality can be produced at a high speed.
In this way, the above-mentioned liquid jet recording process has excellent features, but it is necessary for a higher speed recording of such images of high resolution and high quality that the number of the liquid droplets ejected from one orifice per unit time (N.sub.o), that is, the liquid droplet ejecting efficiency, is increased.
In short, according to the above mentioned liquid jet recording process, bubbles are generated by a heat action and the abrupt increase and decrease of the volume causes the corresponding abrupt change of state and thereby, liquid droplets are projected from the orifice of the recording head to effect recording. It is necessary to increase N.sub.o by shortening the time for repeating the increase and decrease in volume (improvement in the liquid droplet ejection repeating property). It is a proposed to increase the decaying speed of the increased bubble volume which is rate controlling stage, for the purpose of improving said liquid droplet ejection repeating property.
For example this can be effected by providing the recording head portion with a cooling means such as Peltier element and the like so as to cool forcibly the heat generating portion of the electrothermal transducer and the liquid and making the decaying curve of bubble volume resulting in increase in N.sub.o.
When the decaying curve of bubble volume is made steep, the above problem can be solved to some extent, but when the curve becomes steeper than a certain value, meniscus of the liquid formed in the vicinity of the orifice retreats too much and air is sucked into the liquid and further, supply of the liquid to the heat actuating portion becomes unstable resulting in insufficient supply of the liquid. As the result, the following drawbacks appear, that is, non-uniform amount of the ejected liquid droplet, irregular ejecting direction, non-uniform liquid droplet ejecting speed, lowering of fidelity of response to recording signals and assurance of response, and lowering of recorded image quality and stoppage of recording.
When such a special cooling means is arranged at the recording head, the recording apparatus becomes complicated and expensive, and, in particular, such disadvantages are remarkable in case of a recording head of a multi-orifice type. Furthermore, in case of a recording head of a high density multi-orifice type, the result is far poorer since a high grade of precision technique is required for manufacturing such recording head from the view points of structure, processing and fabrication and therefore this results in a low yield, high cost and difficult maintenance.
Further, when the above mentioned cooling means is used to effect a forced cooling so as to accelerate reduction of volume of the generated gas, the cooling efficiency is low because the cooling of the bubble is carried out indirectly by cooling the liquid surrounding the bubble. The response of the cooling means is so slow that improvement in the repeating liquid droplet ejecting property is limited. If it is contemplated to increase the cooling velocity, it is necessary to excessively cool the liquid surrounding the bubble. This results in lowering of liquid droplet ejecting property and other disadvantages.
These disadvantages cause unstable supply of the liquid to the heat actuating portion in the recording head, non-liquid volume of ejected liquid droplets, non-uniform speed for ejecting liquid droplets, lowering of fidelity and accuracy of response to recording signals and like, lowering of recording image quality, and stoppage of recording.
In order to improve the liquid droplet ejecting efficiency, it is necessary that heat energy generated by the electrothermal transducer is applied such that the heat energy is effectively consumed for ejecting liquid droplets.
In case of conducting a continuous recording, it is required that the heat energy is repeatedly generated in response to input recording signals with high fidelity and assurance and the generated heat energy rapidly actuates the liquid in the heat actuating portion. In particular, in case of a high speed recording, this repeated actuation should be effected with high fidelity to input recording signals to the electrothermal transducer. Or, in order to improve the quality of recorded images and effect a high speed recording, there are required stabilization of the liquid droplet ejecting direction, preventing the formation of satellite droplets, stable, continuous and long time, repeated ejection of liquid droplets, and improvement in liquid droplet ejecting efficiency (number of liquid droplets ejected per unit time) and the liquid droplet ejecting speed.
In conventional ink jet recording apparatuses, these drawbacks are not fully solved.